The invention relates to a circuit for regulating an electrical parameter while transferring energy between two networks.
The circuit of the invention may be used whenever an electrical parameter needs to be servo-controlled by means of a transfer of energy. It is applicable, in particular, to consumer, aeronautical, and space applications. In space, this type of servo-control is used for platforms (power conditioning), BAPTA control (for "Bearing and Power Transfer Assembly"), attitude control by means of inertia wheels, etc. . . . ), and also for payloads (electrical power supply, aiming control, active thermal control, etc.).
The following functions may be mentioned, inter alia:
platform:
charging/discharging batteries;
energy conditioning by inertia wheels;
power conditioning; and
controlling DC stepper type motors; and
payload:
converters and regulators for equipment;
low voltage electronic power conditioner (EPC) using a solid state power amplifier (SSPA) and high voltage EPC using a traveling-wave tube amplifier (TWTA);
radar and altimeter power supply; and
motor control in pointing mechanisms for antennas, radio meters, lasers, etc. . . . .
There are two ways in which a parameter may be regulated by an electrical structure:
by series or parallel resonance using a transistor or thyristor H bridge; and
pulse width modulation (PWM) control.
In both cases, energy is transferred without metallic isolation whenever it is necessary to combine the advantages of static and dynamic transfer (energy efficiency of better than 90%).
Resonant structures associate an LC circuit with a set of switches constituting H-bridges, with each bridge being connected to the electricity network exchanging energy flow.
In one possible embodiment, the switches are thyristors ("Series-Resonant Energy Convergence With Multi-Segment Current Waveforms For Bipolar Energy Flow" by J. B. Klaassens and J. Van Duivenbode, published in PESC 88 RECORD, April 1988). The LC resonant network is the link between the two networks exchanging energy, with the other networks being disconnected by the switches.
The servo-controlled parameter is generally the voltage of the energy-receiving network.
Another type of application described in the above-mentioned document (PESC 88) defines an energy conditioner between two inertia wheels. Each wheel is represented by an inductor and a current source. The resonant network is completed by capacitance C common to both networks.
These applications are characterized by the flow of sinewave type currents.
PWM structures are characterized by controlling the width of switch pulses and by a flow of triangular wave type currents.
The object of the invention is to reduce electrical losses as much as possible in circuits of this type.
In another prior art document entitled "A Bidirectional High Power Cell Using Large Signal Feedback Control With Maximum Current Conduction Control (MC.sup.3) For Space Applications", published in IEEE 1986, the principle of bidirectional energy transfer is analyzed and control by means of a state variable in a high signal system is described for "smart" PWM, with the advantages of this technique being described for a battery regulator. The large signal analysis and the mathematical module are described by using a DC state variable model over one sampling period. The behavior under MC.sup.3 current control is tested and its equivalent model is verified by simulation.
However, such a circuit provides no metallic isolation: there is no ground decoupling, and this is very important, in particular for obtaining noise immunity.